Validate Radio Button

Hello, my question is how can I validate if any button of my Button Group is selected or not, for example if none is selected send me an error message try with some methods but do not give (it's a form)

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        String nuevonombre = nombre.getText();
        String nuevoapellido = apellido.getText();
        String identificacion = id.getText();
        String telefono = ntelefono.getText();
        String p1 = placa1.getText();
        String p2 = placa2.getText();
        String h=horas.getText();



    Guardardatos guardar = new Guardardatos();
    if (nuevonombre.equals("") || nuevoapellido.equals("")
            || identificacion.equals("") || telefono.equals("")
            || p1.equals("") || p2.equals("")|| h.equals("")) {

        JOptionPane.showMessageDialog(null, "Ningun campo puede quedar vacio");
    } else { //Aqui es donde empieza mi lio
        if (guardar.gettipoc().equals("")==false) {
            if (guardar.gettvehiculo().equals("") == false) {
                guardar.setnombre(nuevonombre);
                guardar.setapellido(nuevoapellido);
                guardar.setid(identificacion);
                guardar.settelefono(telefono);
                guardar.setplaca(p1, p2);

                JOptionPane.showMessageDialog(null, "Los datos han sido guardados");
                this.dispose();
            } else {
                JOptionPane.showMessageDialog(null, "Es necesario seleccionar el tipo de vehiculo ");
            }
        } else {
            JOptionPane.showMessageDialog(null, "Es necesario seleccionar el tipo de cliente ");
        }
    }


}                                        

private void jRadioButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                              
    Guardardatos guardar = new Guardardatos();
    guardar.setTvehiculo("Carro");
}                                             

private void jRadioButton1MouseClicked(java.awt.event.MouseEvent evt) {                                           
    // TODO add your handling code here:
}                                          

private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    this.dispose();

}                                        

private void jRadioButton5ActionPerformed(java.awt.event.ActionEvent evt) {                                              
    Guardardatos guardar = new Guardardatos();
    guardar.tcliente("A");

}                                             

private void jRadioButton6ActionPerformed(java.awt.event.ActionEvent evt) {                                              
    Guardardatos guardar = new Guardardatos();
    guardar.tcliente("B");
}                                             

private void jRadioButton7ActionPerformed(java.awt.event.ActionEvent evt) {                                              
    Guardardatos guardar = new Guardardatos();
    guardar.tcliente("C");
}                                             

private void jRadioButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                              
    Guardardatos guardar = new Guardardatos();
    guardar.setTvehiculo("Camioneta");
}                                             

private void jRadioButton3ActionPerformed(java.awt.event.ActionEvent evt) {                                              
    Guardardatos guardar = new Guardardatos();
    guardar.setTvehiculo("Bus");
}                                             

private void jRadioButton4ActionPerformed(java.awt.event.ActionEvent evt) {                                              
    Guardardatos guardar = new Guardardatos();
    guardar.setTvehiculo("Moto");
}                                             

private void jRadioButton5MouseClicked(java.awt.event.MouseEvent evt) {                                           

    // TODO add your handling code here:
}                                          

/**
 * @param args the command line arguments
 */

// Variables declaration - do not modify                     
private javax.swing.JTextField apellido;
private javax.swing.JTextField horas;
private javax.swing.JTextField id;
private javax.swing.JButton jButton1;
private javax.swing.JButton jButton2;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel3;
private javax.swing.JLabel jLabel4;
private javax.swing.JLabel jLabel5;
private javax.swing.JLabel jLabel6;
private javax.swing.JLabel jLabel7;
private javax.swing.JLabel jLabel8;
private javax.swing.JLabel jLabel9;
private javax.swing.JPanel jPanel1;
private javax.swing.JPanel jPanel2;
private javax.swing.JRadioButton jRadioButton1;
private javax.swing.JRadioButton jRadioButton2;
private javax.swing.JRadioButton jRadioButton3;
private javax.swing.JRadioButton jRadioButton4;
private javax.swing.JRadioButton jRadioButton5;
private javax.swing.JRadioButton jRadioButton6;
private javax.swing.JRadioButton jRadioButton7;
private javax.swing.JTextField nombre;
private javax.swing.JTextField ntelefono;
private javax.swing.JTextField placa1;
private javax.swing.JTextField placa2;
private javax.swing.ButtonGroup tipocliente;
private javax.swing.ButtonGroup tipodevehiculo;